Ok - Schumacher 100/30/2 charger. Napa wet cells 950cc amps both 12 volts. Both batts have been badly abused by me and presumably the previous owner because of long storage and parasitic loads - they have gone dead more than once.

My Schumacher is charging them at 15.5 volts which seems awfully high and it seems to be settling in for a long charge.

Do I have this right? The acid in the batteries uses sulfur. By being discharged for a long time the sulfur has solidified on the lead making it unable to hold a charge as well as it should. By increasing the volts higher than normal the hope is the sulfur will dislodge and redissolve into the battery fluid??? This should lower the ph of the batt fluid and I can get a few years or maybe a summer out of them?

From what I am reading, it sounds like you are doing an equalizing charge. The proper way to determine if the equalizing charge is complete is to take specific gravity readings with a hydrometer about every 10 to 15 minutes. When the readings on each cell are the same for a couple of readings in a row, you should stop charging. Be careful of sparks and open flames on the area around the batteries, they will be gassing like crazy. I have also been told not to equalize for more than two hours.

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I know you believe you understand what you think I said,But I am not sure you realize what you heard is not what I meant

Sorry, brain isn't functioning correctly. Reply should have said take readings about every 1/2 hour to an hour. I also meant to say 12 hours, not two. That's what I get for trying to do more than one thing at a time.

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I know you believe you understand what you think I said,But I am not sure you realize what you heard is not what I meant

To redo the desulfication the battery charger uses ac voltage to clean the lead walls.It takes a loong time to condition the batteries.I have tried doing it a few times but never had the patience..if it does succeed let is know I know in some instances newer chemicals may need to be added.

Well they seem to have charged about 5 or 6 hours each with most of that time up around 15.5 volts. The charger just then went into a charged mode and wouldn’t allow me to do anything else. I did check the one I did yesterday and it was still reading 13.1 volts so I hope that is a sign the batt is still good.

I doubt if that charger is intentionally trying to "de-sulphate" (aka equalize) anything unless you specifically set it up to do that. If it doesn't have a setting or switch for "equalize" or "De-sulphate", it probably doesn't have that feature.

15.5v is high but not out of the question for the bulk charges stage of a flooded cell battery. In bulk charge, the charger attempts to maintain a high current rate and raises the voltage as needed to achieve that. A very low battery, or one that has some internal damage (partially shorted cells) might stay in that mode for a long time. Or forever.

It does have a "de-sulphate" feature but maybe it was just recharging. Either way they seem to be holding a 12.9 volt charge for the last several days in awfully cold temps. I think they are probably still good. I would have guessed that they would have been shot after leaving them "dead" (about 9.8 volts) for weeks.

Cell voltage doesn't tell you much about whether or not a cell has desulfated. You need to measure the specific gravity of the electrolyte using a hydrometer to tell if the sulfur deposits have been restored to sulfuric acid and that the cell has taken more than a surface charge.

Specific gravity is temperature specific. A good hydrometer will have a calibrated float, the best will also have a thermometer so you can compensate for the electrolyte temperature. The multi-ball type of hydrometers are about useless.

An equalizing charge serves two purposes. First, since all of the cells are in series, they all get the same amount of charging current. If one cell is weaker than the rest, it will charge to it's rated voltage first, and the battery will indicate full voltage before the other cells reach full charge. The higher equalizing voltage forces the current flow to continue, letting all of the cells reach 100% charge.

Second, the bubbling mixes the electrolyte, reversing the stratification layers that can form. Sulphuric acid is heavier than water, so without periodic equalization it tends to settle towards the bottom of the cells, leaving inactive water at the top.

I have a similar Schumacher charger. I think you have the right charger for the easy way out! Great charger. I believe it will automatically do the desulfunation cycle when needed. It is a "smart" charger. If you have the owners' manual, it will provide details on how it does this.

For about $85 each you can replace those automotive batteries with actual deep cycle 6 volts and have much better battery performance than your existing batteries did when new. Even though they hold a charge they have undoubtedly suffered some damage by being allowed to go flat. Go to costco or Sams club and get 2 GC2s. Any battery that lists Cold Cranking Amps is not a deep cycle battery.

For about $85 each you can replace those automotive batteries with actual deep cycle 6 volts and have much better battery performance than your existing batteries did when new. Even though they hold a charge they have undoubtedly suffered some damage by being allowed to go flat. Go to costco or Sams club and get 2 GC2s. Any battery that lists Cold Cranking Amps is not a deep cycle battery.

There are many "Methods" of desulfating. one is a controlled overcharge, exactly the same as an equalization charge.. Does it work? I have not dug into it that deep but I believe it does based on what I've heard.

Some use far lower current and pulse the charge so as to vibrate the sulfer back into solution.. I'm not as sure this works but the makers claim it does.

All in all I'd say let your charger do it's thing.

The Acid does not "Use sulfur' it is Sulfuric acid, Di9luted (by distilled water) Sulfuric acid.

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Nothing adds excitement like something that is none of your businessMy Home is where I park it.

By the way, my battery guy said it was wired for 24 volts but he could have been wrong as he only took a quick look at it. I do know that diesels are started with 24 volts sometimes at least.

In the end these seem to be holding a nice charge in the cold northeast so I am going to hang onto them for the time being. I personally think my smart charger did some type of desulfication as it is setup to do that automatically. It is the perfect charger for dopes like me .

The auxiliary starter gives me the confidence not to sweat it if they won’t start it themselves. When I need that a time or two I will head to the batt store.